diff --git a/NEWS.md b/NEWS.md
index f2478a5d..b03786d8 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -89,9 +89,11 @@ Red Panda C++ Version 2.27
   - enhancement: Correct tab orders for all setting pages/dialogs.
   - enhancement: Shortcut key for buttons in find/replace and "find in files" dialogs.  
   - enhancement: Auto define macro "_DEBUG" for "Debug" compiler set(like visual studio).
-  - enhancement: Suggest macro names after "#ifdef"/"#ifndef".
+  - enhancement: Suggest macro names after "#ifdef"/"#ifndef"/"#undef".
   - enhancement: If contents from stderr are logged into "Tools Output" panel, add problem case name info to the log. 
   - fix: In split screen mode, editor on the right can't be correctly found by commands.
+  - fix: Remove duplicated macro defines make it's lost in the parse result.
+  - fix: An undefined macro is still missing the the parse result after #undef is removed.
     
 Red Panda C++ Version 2.26
   - enhancement: Code suggestion for embedded std::vectors.
diff --git a/RedPandaIDE/compiler/compiler.cpp b/RedPandaIDE/compiler/compiler.cpp
index d3566b07..d9dd4d9a 100644
--- a/RedPandaIDE/compiler/compiler.cpp
+++ b/RedPandaIDE/compiler/compiler.cpp
@@ -452,6 +452,10 @@ QStringList Compiler::getCCompileArguments(bool checkSyntax)
             result << parseArguments(s, macros, true);
         }
     }
+
+    if (result.contains("-g3")) {
+        result << "-D_DEBUG";
+    }
     return result;
 }
 
@@ -493,6 +497,10 @@ QStringList Compiler::getCppCompileArguments(bool checkSyntax)
             result << parseArguments(s, macros, true);
         }
     }
+
+    if (result.contains("-g3")) {
+        result << "-D_DEBUG";
+    }
     return result;
 }
 
diff --git a/RedPandaIDE/compiler/filecompiler.cpp b/RedPandaIDE/compiler/filecompiler.cpp
index bf9afd65..e50e58e3 100644
--- a/RedPandaIDE/compiler/filecompiler.cpp
+++ b/RedPandaIDE/compiler/filecompiler.cpp
@@ -138,9 +138,6 @@ bool FileCompiler::prepareForCompile()
     default:
         throw CompileError(tr("Can't find the compiler for file %1").arg(mFilename));
     }
-    if (mArguments.contains("-g3")) {
-        mArguments << "-D_DEBUG";
-    }
     if (!mOnlyCheckSyntax)
         mArguments += getLibraryArguments(fileType);
 
diff --git a/RedPandaIDE/compiler/projectcompiler.cpp b/RedPandaIDE/compiler/projectcompiler.cpp
index f4891244..b003ff84 100644
--- a/RedPandaIDE/compiler/projectcompiler.cpp
+++ b/RedPandaIDE/compiler/projectcompiler.cpp
@@ -225,12 +225,7 @@ void ProjectCompiler::writeMakeDefines(QFile &file)
     // Get list of applicable flags
     QStringList cCompileArguments = getCCompileArguments(false);
     QStringList cxxCompileArguments = getCppCompileArguments(false);
-    if (cCompileArguments.contains("-g3")) {
-        cCompileArguments << "-D_DEBUG";
-    }
-    if (cxxCompileArguments.contains("-g3")) {
-        cxxCompileArguments << "-D_DEBUG";
-    }
+
     QStringList libraryArguments = getLibraryArguments(FileType::Project);
     QStringList cIncludeArguments = getCIncludeArguments();
     QStringList cxxIncludeArguments = getCppIncludeArguments();
diff --git a/RedPandaIDE/editor.cpp b/RedPandaIDE/editor.cpp
index 69305ce5..e807501e 100644
--- a/RedPandaIDE/editor.cpp
+++ b/RedPandaIDE/editor.cpp
@@ -928,7 +928,7 @@ void Editor::keyPressEvent(QKeyEvent *event)
 
                             //last word is a type keyword, this is a var or param define, and dont show suggestion
                             return;
-                        } else if (lastWord == "#ifdef" || lastWord == "#ifndef") {
+                        } else if (lastWord == "#ifdef" || lastWord == "#ifndef" || lastWord == "#undef") {
                             processCommand(QSynedit::EditCommand::Char,ch,nullptr);
                             showCompletion(lastWord,false, CodeCompletionType::Macros);
                             handled=true;
diff --git a/RedPandaIDE/parser/cpppreprocessor.cpp b/RedPandaIDE/parser/cpppreprocessor.cpp
index 09aadb6c..254273bd 100644
--- a/RedPandaIDE/parser/cpppreprocessor.cpp
+++ b/RedPandaIDE/parser/cpppreprocessor.cpp
@@ -35,6 +35,7 @@ void CppPreprocessor::clear()
     //used by parser even preprocess finished
     mIncludesList.clear();
     mFileDefines.clear(); //dictionary to save defines for each headerfile;
+    mFileUndefines.clear(); //dictionary to save undefines for each headerfile;
     mScannedFiles.clear();
 
     //option data for the parser
@@ -175,16 +176,28 @@ void CppPreprocessor::preprocess(const QString &fileName)
 
 void CppPreprocessor::invalidDefinesInFile(const QString &fileName)
 {
+    //remove all defines defined in this file
     PDefineMap defineMap = mFileDefines.value(fileName,PDefineMap());
     if (defineMap) {
         foreach (const PDefine& define, *defineMap) {
             const PDefine& p = mDefines.value(define->name);
             if (p == define) {
                 mDefines.remove(define->name);
+                PDefine p2 = mHardDefines.value(define->name);
+                if (p2)
+                    mDefines.insert(define->name, p2);
             }
         }
         mFileDefines.remove(fileName);
     }
+    //restore all defines undefined in this file
+    PDefineMap undefineMap = mFileUndefines.value(fileName,PDefineMap());
+    if (undefineMap) {
+        foreach (const PDefine& define, *undefineMap) {
+            mDefines.insert(define->name, define);
+        }
+        mFileUndefines.remove(fileName);
+    }
 }
 
 void CppPreprocessor::dumpDefinesTo(const QString &fileName) const
@@ -312,6 +325,7 @@ void CppPreprocessor::removeScannedFile(const QString &filename)
     mScannedFiles.remove(filename);
     mIncludesList.remove(filename);
     mFileDefines.remove(filename);
+    mFileUndefines.remove(filename);
 }
 
 QString CppPreprocessor::getNextPreprocessor()
@@ -505,12 +519,21 @@ void CppPreprocessor::handleUndefine(const QString &line)
     if (define) {
         //remove the define from defines set
         mDefines.remove(name);
-        //remove the define form the file where it defines
         if (define->filename == mFileName) {
+            //remove the define form the file where it defines
             PDefineMap defineMap = mFileDefines.value(mFileName);
             if (defineMap) {
                 defineMap->remove(name);
             }
+        } else {
+            // add it to undefine map
+            PDefineMap undefineMap = mFileUndefines.value(mFileName);
+            if (!undefineMap) {
+                undefineMap = std::make_shared<DefineMap>();
+                mFileUndefines.insert(mFileName,undefineMap);
+            }
+            if (!undefineMap->contains(name))
+                undefineMap->insert(name, define);
         }
     }
 }
diff --git a/RedPandaIDE/parser/cpppreprocessor.h b/RedPandaIDE/parser/cpppreprocessor.h
index e90af39d..aee839a8 100644
--- a/RedPandaIDE/parser/cpppreprocessor.h
+++ b/RedPandaIDE/parser/cpppreprocessor.h
@@ -274,6 +274,7 @@ private:
     //used by parser even preprocess finished
     QHash<QString,PFileIncludes> mIncludesList;
     QHash<QString, PDefineMap> mFileDefines; //dictionary to save defines for each headerfile;
+    QHash<QString, PDefineMap> mFileUndefines; //dictionary to save defines for each headerfile;
     QSet<QString> mScannedFiles;
 
     //option data for the parser